Add `packages` parameter to `Isolate.spawnUri`.

runtime/lib/isolate_patch.dart

Index: runtime/lib/isolate_patch.dart
diff --git a/runtime/lib/isolate_patch.dart b/runtime/lib/isolate_patch.dart
index e3dbec151739f367514c40226c3d82cf31672df5..9142ff9bb88639bf78440af2ad249f5dd196f8a7 100644
--- a/runtime/lib/isolate_patch.dart
+++ b/runtime/lib/isolate_patch.dart
@@ -306,11 +306,17 @@ patch class Isolate {
 
   /* patch */ static Future<Isolate> spawnUri(
       Uri uri, List<String> args, var message,
-      {bool paused: false, bool checked, Uri packageRoot, bool errorsAreFatal,
-       SendPort onExit, SendPort onError}) {
+      {bool paused: false,
+       bool checked,
+       Uri packageRoot,
+       Map<String, Uri> packages,
+       bool errorsAreFatal,
+       SendPort onExit,
+       SendPort onError}) {
     RawReceivePort readyPort;
     try {
       // The VM will invoke [_startIsolate] and not `main`.
+      // TODO: Handle [packages].
       readyPort = new RawReceivePort();
       var packageRootString =
           (packageRoot == null) ? null : packageRoot.toString();